Are you using primer ? Yes, I used primer
I put the glue on and let it melt the PVC a bit 30 seconds or so, Then Twist and hold for about 3 Minuets. Holding that long may be overkill but it works and does not move. I did not hold that long, but I did twist until it wouldnt twist any more and also made sure the pipe inserted all the way
There are different glues for different PVC types. The correct glue should melt the pipe together. Found that out the hard way one time...definitely the right glue.
Do you have couplings, or are they built into the pipe ? I used couplings
The Belled PVC pipe is much better for the suction line.
Sometimes the Couplings to not match the Pipe you are using, and the Glue does not devolve the different plastics properly.
Good Luck.